At a quick look, I don't see anything that would be impossible to integrate in Dadod's schematic. It would be an awfully designed IC, though.
Don't forget to include in the discussion the development cost and the market of this new IC.
There are already current feedback amplifier ICs with the same or better performances (including the output current). Check out LT1206 (250mA) and LT1210 (1Amp) CFAs, they cost less than $20 in singles.
Oh well, not such a fine day after all: it was mostly ice, which I dislike. I did find 1 single trail with some fresh powder, about a foot or so, ungroomed as I like, and I did it 10 times.
Yes, Geneva is a priviledged location: 1 hour to Chamonix, 2-3 hours to Verbier and Zermatt. But I'm afraid these places are fading fast with the global warming: we barely had any snow this year.
I built a headphone amp using a LME 49600 with a LM4562 driving it in side the opamp feedback loop. I know the distortion was ppm level and the peak output current - not that you’d need it with 32 Ohms phones - was c. 1A. On normal phones, 2 or 3 volts peak is ear splitting.
TI also do a very nice wide band CFA amplifier with c. 700 mA output that I currently use. Distortion also ppm level (measured).
In specialist audio cases where you may want the last ounce of noise a discrete circuit may give that to you (MM or MC amp for example) but to hear the difffence in a well designed system you have to have your ear next to the tweeter. Does it matter when the stylus hits the vinyl? No. For line level? No chance.
You should not dismiss IC solutions like this. There is every engineering reason to in fact adopt exactly the opposite position with small signal stuff nowadays.
Maybe the old guys still have a chance. Many moons ago, JC told me, regarding SS amplifications: "... but they sound different...", that immediately rang a bell, and I said "... you mean, like 6L6's sound different than KT66's? But everybody knows that...". Maybe we're less dogmatic, contrary to popular belief.
Don't get me wrong: I do believe the basics have to be done right. But after you fix all the known metrics such as frequency response, transient response, THD, IMD, TID, PID, and so on, there still are differences, but often times we don't know what they are and how to measure them.
OTOH, stating 2 items that meet the basic criteria sound the same is presumptuous.
Which actual example of that case can you cite, 2 components that presumed to sound the same based on basic criteria but turned out not?
Have you? I was not aware you experimented with high bandwidth, high slew rate, high output current, current feedback ICs.
Details please?
My Parasound JC-3 does not sound as good as my Vendetta Discrete phono stage. How do I know? Because I compared both with the same amp, loudspeaker, and phono input.
I did, at the same time, (this is for Ed) compare the AD797 with the Natl device, and found them sounding 'different' but equally good. Another IC failed in the comparison.
I did, at the same time, (this is for Ed) compare the AD797 with the Natl device, and found them sounding 'different' but equally good. Another IC failed in the comparison.
I spent some time talking to a 'high end' audio designer who designed a discrete headphone amp that turned to be very popular, and only costs around $3500.
Turns out the main advantage we could agree on is the ability to tune the low order H2 and H3 to taste, while keeping higher order harmonics very low. Might be possible to do with a composite design with a discrete input stage followed by an opamp and maybe a low distortion buffer. No need though. High end consumers apparently have the wherewithal to buy what they want, and they happen to like their carefully crafted HD in fully discrete form.
So, I ask what if you make a phono stage tuned like that, a preamp like that, and a power amp too, what happens if someone decides to use them all in the same reproduction system? He said, "I am aware of that risk." Then followed with a tone fading from exasperation to resignation, "You have to pick you poison."
Turns out the main advantage we could agree on is the ability to tune the low order H2 and H3 to taste, while keeping higher order harmonics very low. Might be possible to do with a composite design with a discrete input stage followed by an opamp and maybe a low distortion buffer. No need though. High end consumers apparently have the wherewithal to buy what they want, and they happen to like their carefully crafted HD in fully discrete form.
So, I ask what if you make a phono stage tuned like that, a preamp like that, and a power amp too, what happens if someone decides to use them all in the same reproduction system? He said, "I am aware of that risk." Then followed with a tone fading from exasperation to resignation, "You have to pick you poison."
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Not much to add here, since there are only 15V rails there are several complementary IC processes that could do this function exactly (you would not do it this way though). The current sources for one are not temperature stable (might not matter much here). The discrete part is not doing much work so the major benefit is the separation of power out to another chip. I think Jan did this with an AD844 which has access to the gain node.
The NPN/PNP datasheets are a cut and paste of each other which I find a little hard to believe in reality. Operating at widely different Vce's would reduce the benefit somewhat anyway.
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Hi,
Let me back up a second.... of course you can add an out-board power stage... bipolar or fet and get a lot of drive to low Z loads. but, that isnt just a ic opamp.
Now with the IC output buffer -- I measured it long ago by itself. It only has good dc specs -- ac is terrible. So bad, in fact, it can ONLY be used in a high negative (GNFB) feedback opamp configuration. Dont know how that combination would sound but I think you can do better with a discrete output stage added on to ic opamp.
I did say with small signal and high Z loads the IC opamp is generally fine. At least the newer CFA types are interesting to me. Maybe for HPA, the newer CFA you mention sounds very good with low Z loads and with Planar Magnetic type. ??
On the other hand, I dont know that 4 cheap transistors and 4 more for a really good output buffer isnt even cheaper than a really good ic opamp with 4 transistor out board buffer. AND, have total control over FB levels/margins etc.
THx-RNMarsh
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I encourage you to use the ignore function to eliminate the twits.
It immediately raises the IQ of this thread by at least 30 points.
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How would you do it as an IC and what wpuld you change for this discrete design?
A data sheet cut and paste job!!!
Can I mention loudspeaker specifications? Ever see a 1,000 watt woofer get fed 1,000 watts? Much more impressive failure mode than I have ever seen on an opamp.
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